In general, when a cargo that is used to transport articles such as grain, oil, gas and the like is manufactured, a work is performed in a polyhedral block-like three-dimensional hollow frame. When the work is performed in the hollow frame, due to a spatial restriction including the installation of a precision measuring instrument in the hollow frame, a worker can only perform manual measurement using a measuring tape.
Accordingly, when the work is performed within the hollow frame, an error is cumulated due to inaccurate measurement, and thus a correction work needs to be performed several times. For this reason, the work progress or productivity may be deteriorated.
Furthermore, in manufacturing the three-dimensional hollow frame, the works such as attachment, welding, grinding, and painting need to be performed on each surface of the hollow frame. To this end, a large structure is installed in the hollow frame, which causes a signal from an indoor GPS not to be appropriately transmitted. In addition, the indoor GPS needs to be repeatedly installed and removed at many places in the hollow frame to measure the coordinate of the hollow frame. In this case, however, since a plurality of local coordinate frames is generated, there is a difficulty in managing the data of the measured coordinates.
Furthermore, in the three-dimensional hollow frame, when the surfaces are bonded to each other to form a space, a part to be welded may be located at a higher place. Accordingly, a scaffold is temporarily provided at the inner wall of the hollow frame so as for a worker to get up the scaffold and perform the welding. In this case, however, the laser signals may be shielded by the scaffold. Therefore, all of the places to be measured may not be measured using the indoor GPS that is fixedly installed at a place. For this reason, it is necessary to perform the measurement while moving the indoor GPS at several places, which causes the generation of the local coordinate frames. As a result, there may be a difficulty in collectively managing the measurement data.